Various methods and systems have been developed for command guidance of air-to-ground or ground-to-ground missiles. Some of these systems comprise an infrared tracker which senses the deviations of a missile from the line-of-sight to a selected target and a command signal processor which provides signals to the missile to cause it to fly along this path. The operator's sole function is to maintain the line-of-sight path on the target, with the aid of a sight aligned to the tracker, whereby the missile is caused to impact the target. Such a system is disclosed in U.S. Pat. No. 3,366,346. Unmodulated sources as well as modulated tungsten flares, xenon lamps, or other sources of infrared are used to provide a unique infrared signature (beacon) on the missile to aid the tracking capability of the tracker. It is desired that these systems function precisely under adverse conditions existant on the battle field. Certain performance capabilities of systems now known and used are limited by the low frequency modulation capabilities of these beacons, and by their spectral broadness.